Small port 4age with big port cams - Timing & Injector questions

Small port 4age with big port cams - Timing & Injector questions

So I just finished doing a full rebuild on my small port 4age w/ big port cams. (I remember reading years ago about this, and how it gave a mild performance upgrade)

Currently the engine is running on all stock big port electronics including injectors. Also, has a TRD .8mm head gasket

Engine seems to be running fine and sounds good, starts good, idles well. but the timing it at 30 degrees. Like on the little timing mark area you have the spread from +15,+10, +5, 0, -5. and I'm easily around +30 maybe even +40. If I move the distributor ahead a tooth and its idling at like 3500rpm and drop it back a tooth and it wont start at all.Is this because I'm running big port electronics and injectors? or maybe the cams are ground with a different timing setting from big port to small port?

If I swap to the small port injectors and keep the big port harness I need to cut and loop(bypass) the wires on the resistor box that mounts near the passenger strut tower under/near the air box?

I've looked around and used the search function and maybe the info I'm looking for is lost on the old forum?

Just wanted to see if this is all normal, or if I'm dialing in my engine at a wonky setting that will cause damage down the road

Re: Small port 4age with big port cams - Timing & Injector questions

Posted: Mon Sep 11, 2017 1:00 pm

by wewerica

I have smallport head with bigport cams but I dont have that kind of issue Idling at 10deg @ 800rpm like a charm

Re: Small port 4age with big port cams - Timing & Injector questions

Posted: Mon Sep 11, 2017 3:12 pm

by jondee86

Could be a vacuum leak, so to be clear...- Are you using the factory AE86 RWD intake manifold with a bigport to smallport adapter plate ?- Or did you just bolt the RWD manifold to the smallport head ?- Or have you cut-n-shut the smallport manifold ?- Or is the engine in a FWD car ?

Otherwise. what is the idle speed when the timing is at 30 deg ? It is not unknown for the outer ring on the OEM crankshaft pulley to move, so when you set the engine to Top Dead Centre on cylinder #1(with a screwdriver or similar down the spark plug hole) does the notch on the pulley line up with the zero deg mark on the scale ?

Cheers... jondee86

Re: Small port 4age with big port cams - Timing & Injector questions

Posted: Tue Sep 12, 2017 4:55 am

by davew7

Another vote for jondee86's [Outer ring on the OEM crankshaft pulley has moved.]Dave W

Re: Small port 4age with big port cams - Timing & Injector questions

Posted: Tue Sep 12, 2017 9:38 am

by quietskaterguy

jondee86 wrote:Could be a vacuum leak, so to be clear...- Are you using the factory AE86 RWD intake manifold with a bigport to smallport adapter plate ?- Or did you just bolt the RWD manifold to the smallport head ?- Or have you cut-n-shut the smallport manifold ?- Or is the engine in a FWD car ?

Otherwise. what is the idle speed when the timing is at 30 deg ? It is not unknown for the outer ring on the OEM crankshaft pulley to move, so when you set the engine to Top Dead Centre on cylinder #1(with a screwdriver or similar down the spark plug hole) does the notch on the pulley line up with the zero deg mark on the scale ?

Cheers... jondee86

Sorry, I tried to cover all parts but missed a few things. I'm using the T3 adapter plate so I'm still running the big port manifold. Its in a RWD car

Idle speed starts around 2000rpm, sometimes as much as 2500rpm, but after the engine warms up its idling around 1100rpm, and sometimes as low as 700rpm

I will test the top dead center theory today if I have a minute and report back on that as well. Haven't heard of the notch moving before, I didn't know the ring its on was a separate piece.

Re: Small port 4age with big port cams - Timing & Injector questions

Posted: Tue Sep 12, 2017 2:39 pm

by jondee86

quietskaterguy wrote:Idle speed starts around 2000rpm, sometimes as much as 2500rpm, but after the engine warms up its idling around 1100rpm, and sometimes as low as 700rpm

Sounds pretty much normal then You have the OEM thermostatic idle-up valve working.That will give you a cold start idle of around 2200rpm, dropping to around 900rpm once the engine is fully warmed up.

You can't check the idle rpm until the engine is fully warmed up, and then if you put your light on the pulley the mark should be hovering around 16-17 deg. You also need to adjust the dissy so that the engine is running at around 900rpm when you check. Note that there is an "official" way to set the idle by shorting the diagnostic plug. Then the timing is set to 10deg. Doing it without shorting the diagnostic plug you set to 16-17deg as above.

If you can set the idle timing so the engine idles nice when fully warm and see 16-17deg on the scale, then you are done. But if you can only get it to idle nice at something way different, then check to see if the outer ring (rubber mounted) of the pulley has moved.

Once you have set the timing, rev the engine with the light still on the pulley and watch the notch on the pulley disappear to the left

Cheers... jondee86

Re: Small port 4age with big port cams - Timing & Injector questions

Posted: Tue Sep 12, 2017 3:12 pm

by jondee86

quietskaterguy wrote:Just wanted to see if this is all normal, or if I'm dialing in my engine at a wonky setting that will cause damage down the road

What you have now is basically a high compression bigport engine, so it should run fine with bigport injectors and electronics. You need to get someone with a wideband and a tailpipe sniffer to check your air/fuel ratios in case the engine is running lean.

The factory narrow band O2 (if fitted to your car) and factory ECU should be able to keep the AFRs pretty good, but you may need to up the fuel pressure a fraction to help it do its job. That means fitting an adjustable fuel pressure regulator.

If you have an injector resistor pack that means you have low resistance injectors. The smallport usually runs high resistance injectors without a resistor pack, so you are correct about bypassing the resistor pack if you use smallport injectors. You will also need to change the injector clips. Another possibility would be to see if you can locate some low resistance Denso injectors with a slightly higher capacity. Then you have an easy "drop in" installation with no other changes required.

Cheers... jondee86

Re: Small port 4age with big port cams - Timing & Injector questions

Posted: Wed Sep 13, 2017 9:21 am

by quietskaterguy

Sounds good Jon,

I will double check all this info tonight for sure. I'll look into the FRP but I think I'm fine here. My plan was to swap the injector pig tails after I had the engine dialed in. I didn't want to do it before the swap and spend days trying to figure our why it wont run when its something I physically changed. I'll look into other options for the injectors though. Any leads on what might work? Part numbers or cars they came in?

To be be honest, I haven't every done anything with injectors besides swapping in newer ones or swapping pig tails to use other ones. do all Densos have the same plug style on them and so most/all are interchangeable?

Thanks Again Jon. this group is lucky to have you around!

Re: Small port 4age with big port cams - Timing & Injector questions

Posted: Wed Sep 13, 2017 3:38 pm

by jondee86

quietskaterguy wrote: Do all Densos have the same plug style on them and so most/all are interchangeable?

The same "oval" style of plugs are used on most of the older Toyota/Denso injectors, but the hi and lo resistance plugs are coded differently. The little fins on the side of the plug are in a different position, so you can swap lo for lo or hi for hi but not swap hi for low without changing the clips.

The reason you need to check the AFR's is that raising the compression can increase the possibility of detonation if you don't have the ability to tune the ignition map. One way of staying safe is to use the highest octane pump gas available in your area. You could dial the timing back on the dissy, but this will drop power and kind of defeats the benefits of raising the compression.

Detonation is more likely to occur if the engine is running lean. So while not strictly necessary when the only modification to the engine is raising the compression, running a slightly rich mixture is a good idea for safety. You can do this by raising the fuel pressure or by fitting a higher capacity injector. Depending on who you believe, the factory bigport injector is either 180, 185 or 200cc/min and the factory smallport around 235cc/min.

This messed up chart from Club4AG gives an idea of lo resistance options ... http://club4ag.com/faq_and_tech_pages/T ... Denso.htmlI'd suggest that you check the part numbers on your existing injectors and then see if you can locate some a little larger, say an extra 20cc/min. But don't do this until you get your AFR's checked at a tuneup garage or dyno shop. Your ECU might already be keeping you safe without needing more fuel.

PS: You might like to consider installing a wideband O2 sensor and gauge if you are planning further engine modifications

Re: Small port 4age with big port cams - Timing & Injector questions

Posted: Thu Sep 14, 2017 7:07 am

by oldeskewltoy

There is another injector option........

Late 80s Honda Accord, and Prelude 2.0i engines uses low ohm (peak and hold) 240cc injectors. These are the go to injector I recommend with mild builds.

Re: Small port 4age with big port cams - Timing & Injector questions

Posted: Thu Sep 14, 2017 5:48 pm

by jondee86

Seeing as it is a quiet day, I thought that I would try and clarify a couple of points arising out of the various comments that I have made above. In particular these apply when mixing and matching components, or modifying engines.

Engine Control Unit (ECU) Each engine when it leaves the factory has the ECU optimised to provide the best all round performance possible with the stock components. This means that the ignition and fuel maps are tuned to work with the stock compression ratio, intake, exhaust, cams etc. When the engine is modified and the ECU cannot compensate for the changes in operating conditions, the ignition and fuel maps are no longer optimised.

Planning ModificationsThere is very little point in making random modifications in the hope that you will get lucky and get a big gain from some shiney bolt-on part. To get a decent performance gain from your investment of time and money, you need to have a PLAN. Raising the compression is a worthwhile modification, but to gain full benefit from increased compression you need to add other ingredients like cams, headwork, intake and exhaust improvements. And once you go there, a programmable ECU is pretty much mandatory.

How to make more POWERThere is only one way to make more power, and that is to increase the amount of air and fuel that the engine burns. Read that again (you didn't think I was going to tell you how to modify your engine did you ??)

Raising CompressionThis is one of the stepping stones on the path to more power. Raising compression with no other modifications does not increase power by any significant amount (because it does not increase airflow). However, it does lay the groundwork for the later addition of cams, carbs, ITB's, headers etc.

Increasing FuelIn the absence of any modifications that increase airflow, adding more fuel will almost certainly cause the engine to run rich and lose power. Fitting larger injectors or a higher capacity fuel punp without other supporting modifications is a waste of time and money.

Say... WUT ?? Up above you suggested the OP should look at going to larger injectors !!! Correct, but you will note I emphasised the point that he should check what AFR's the engine is running before doing anything to change fueling. The intake and compression ratio of his engine has changed, so the fuel and ignition maps in the factory ECU are no longer optimised, which means that the engine could be running a little leaner (or richer) than ideal.

Just thought I would add that in case anyone was thinking that a "500hp Walbro" is going to make their car faster

Cheers... jondee86

PS: Because you read all that long post I have added a pic of a performance throttlebody that would look good in your car VVVVVVVVVVVVV

Re: Small port 4age with big port cams - Timing & Injector questions

Posted: Fri Sep 15, 2017 9:39 am

by mad_86

haha! lol very informative Jondee

i also have the same set up but with smallport head w/hi injectors pigtails (buy new ones)

check for vacuum leaks, a good way to check is to let the motor warmed up then at idle take a spray bottle with water and lightly spray around the intake/adaptor plateand also around throttle body or where air can escape

if there is a leak the idle would rise abit, you should be able to hear the revs go up = vacuum leak

no change =no leak

im in the process of having a wideband bung welded in,

Re: Small port 4age with big port cams - Timing & Injector questions

Posted: Fri Sep 15, 2017 2:34 pm

by oldeskewltoy

Love the throttle bodies... excuse me throttle body....

But I have a few misgivings... in particular "optimised"... back in 1984?? Optimized FOR 1984 is different, but I'm not whole-y sure your audience understands the level of "crude" we are dealing with.........

Re: Small port 4age with big port cams - Timing & Injector questions

Posted: Fri Sep 15, 2017 4:34 pm

by jondee86

All things are relative I guess I could have said that the factory matches the components they build into the car when it leaves the factory. The compression ratio, injector size, spark plugs, pollution control devices and safety features are selected to suit the intended market. The factory ECU is tuned to give acceptable performance under a wide range of driving conditions while ensuring that the engine remains safe and reliable for a long time with minimal maintenance.

The car also has to meet local noise, economy and air pollution regulations (where they exist) while running on whatever gasoline is available locally. On top of this there are new car warranty obligations that have to be met even if the car is abused.

No easy task, and to meet these goals factory engineers are forced to leave some performance on the table. The OEM ECU will be tuned with more fuel and less ignition than required for maximum performance. This leaves something to be gained from fitting an aftermarket ECU, but of course then your warranty is voided.

In 1985 the AE86 (depending on market) did not have a knock sensor, an O2 sensor or many of the fault detection and "save your engine" sensors fitted to modern cars. And in that way it could be considered to be crude. But the actual fuel and ignition mapping was remarkably similar to that seen in basic aftermarket ECU's today. The OEM ECU idled smoothly once up to temperature, started easily and had good on and off throttle transitions.

But getting back to the point I was trying to make in my previous post, when the 4AGE changed from bigport to smallport, many of the engine basics changed. And the OEM ECU also changed to match the new engine configuration. So while it is possible to run a smallport on a bigport ECU, or a 4AGTE on a GZE ECU, or just about anything on a Honda ECU... THAT DOES NOT MAKE IT A GOOD IDEA !!!

Well... not unless you have amazing skilz and don't mind spending a lot of time and money building something that runs almost as well as a factory setup

Cheers... jondee86

Re: Small port 4age with big port cams - Timing & Injector questions

Posted: Fri Sep 15, 2017 7:24 pm

by Rogue-AE95

jondee86 wrote:or just about anything on a Honda ECU... THAT DOES NOT MAKE IT A GOOD IDEA !!!

Well... not unless you have amazing skilz and don't mind spending a lot of time and money building something that runs almost as well as a factory setup

I disagree somewhat with this. Besides my All-Trac, I also own a Honda, which I temporarily fitted with a D15Z1 engine (considered a real POS in the Honda scene). I bought the engine from a guy who rebuilt it and set it up with a turbo, then tuned a programmable Honda ECU to get the best gas mileage out of it. The D15 engine is going into a 3rd car of mine, once I get it fixed up, so I'm testing out this low-mileage engine in my other Honda. Originally when I swapped in the engine I used a stock fuel map for it, but was getting worse mileage than that car's original engine (which needs a rebuild).

So I put the guy's tune on a programmable ECU, and even though I'm not yet running the turbo, I'm getting much better mileage and even more power out of the 92 HP-rated weakling engine. It's all in the monitoring and tuning, I guess. The guy I bought the D15 engine from did a lot of tinkering with the tuning to get it just right.

Re: Small port 4age with big port cams - Timing & Injector questions

Posted: Fri Sep 15, 2017 8:59 pm

by jondee86

Rogue-AE95 wrote:I disagree somewhat with this.

From what you just wrote it is fairly obvious that you are not a starry-eyed noob starting out to turn a $300 Corolla into a dream machine I accept that almost anything can be made to work by someone with a good understanding of how the internal combustion engine function,s, and how automobile electrical and control systems work. My comments are not aimed at you or anyone who has already attained a black belt in the Zen of Car Mods

My remarks are intended to perhaps make the Path to Enlightenment less hazardous for those folk starting out on their first project. Doing an engine swap with a fully stock engine, accessories, ECU and harness is always going to go better than trying to fit together a bunch of loose parts gathered from half a dozen different engines. I cringe when I see people paying good money for used pistons and rods to put into a bare block with unknown history.

And how many folk rely on matching the colour of wires when mixing and matching harnesses from different model cars, when they should be working with a multimeter and wiring diagrams. The Path to Enlightenment is not easy... but old cars are a great place to start as they are mechanically simple and the electrics are easy to understand. Nothing builds confidence like success with your first modification or repair, no matter how small.

Once the basics have been mastered and a persons understanding of how stuff works grows, then is the time to start looking for more ambitious projects. I know perfectly well that it is possible to turbo a bigport engine and run it on the factory ECU with a few other tricks and mods. But the guy who did it was on his third engine before he got one to stay running for more than a couple of days

Cheers... jondee86

Re: Small port 4age with big port cams - Timing & Injector questions

Posted: Sat Sep 16, 2017 6:58 am

by Rogue-AE95

Gotcha I don't think I've reached blackbelt status quite yet, though The Honda side of things is much easier because so much has already been done, it comes down to either riding on the shoulders of someone else (like me buying that engine and using the tune for it) or following along with what someone else has done. Of course one should always have a custom built engine tuned after getting it together.

I remember reading once about someone on the old forum saying how they had so many hours (hundreds maybe?) into tuning their built engine and it wasn't right yet. I can't imagine a competent tuner having so much trouble getting it just right. Unless the tuner was the guy in question and didn't know what he was doing, or he was changing his mind about how he wanted it to run. I keep hearing about how the 16v 4A-GE is such a simple engine. How can tuning it take dozens of hours? Unless you're just learning how to DIY and you're playing it safe (as you should).

Re: Small port 4age with big port cams - Timing & Injector questions

Posted: Sat Sep 16, 2017 3:19 pm

by jondee86

As a DIY tuner I can confirm that it is a long and time consuming process to road tune a programmable ECU. Getting the engine to run is relatively easy, but getting it to run as well as a factory tuned ECU is much more difficult. Because of the cost of dyno time and professional tuning, often it is only the WOT condition that gets tuned. After all, for many people bragging rights are more important than having a car their mom can drive to the mall

But when you want a car that runs well under all driving conditions, the whole of the ignition and fuel maps has to be tuned, sensors calibrated and multiple compensation tables adjusted for different temperature and load conditions. Whenever you read words like bogging, surging, misfiring, stalling, lacks power, hard starting etc., and the car has a programmanle ECU, there is a good chance that there is a tuning issue.

Playing it safe is the name og the game. My DIY tuning revolves around making a log virtually every time I drive the car, and then using the data from the log to make smalladjustments to maps and compensation tables. After making adjustments I save the revised tune, and I am currently on tune number 103 For the moment I am trying to stay rich and retarded to avoid damaging anything. Eventually when I am happy that I have all the basics reasonably well sorted, I will bite the bullet and have a professional dyno tune for MBT (minimum timing for best torque).

Tuning for MBT on a load holding dyne is the key to unlocking all the performance of an engine. If you don't tune to MBT you are either leaving performance on the table or risking detonation. And as knock detection dosen't work on my engine due to mechanical noise from the s/c, I have to be super cautious on timing to stay out of det.

Cheers... jondee86

Re: Small port 4age with big port cams - Timing & Injector questions

Posted: Sat Sep 16, 2017 4:29 pm

by oldeskewltoy

jondee86 wrote: I have to be super cautious on timing to stay out of det.

Cheers... jondee86

could just as easily used debt..........

Re: Small port 4age with big port cams - Timing & Injector questions

Posted: Sun Sep 17, 2017 2:51 pm

by jondee86

oldeskewltoy wrote:Could just as easily used debt..........

True dat !! My car has already cost a lot to get to the point it is at now, and I wouldn't want to be adding the cost of rebuilding the engine again. In true project fashion, this build has cost more than twice what I expected to spend. The only consolation is that if I average it out over the 15 years I have owned the car, it doesn't seem so bad

Cheers... jondee86

Re: Small port 4age with big port cams - Timing & Injector questions

Posted: Wed Oct 04, 2017 2:25 pm

by quietskaterguy

Sorry I haven't updated anyone on the questions and my results. I've been on the road with work and not able to get into the garage. Hoping I can get in there this week and get the car running smoothly before the snow flies!